Low-Energy Coulomb Excitation for the Shell Model

Low-energy Coulomb excitation is capable of providing unique information on static electromagnetic moments of short-lived excited nuclear states, including non-yrast states. The process selectively populates low-lying collective states and is, therefore, ideally suited to study phenomena such as shape coexistence and the development of exotic deformation (triaxial or octupole shapes). Historically, these experiments were restricted to stable isotopes. However, the advent of new facilities providing intense beams of short-lived radioactive species has opened the possibility to apply this powerful technique to a much wider range of nuclei. The paper discusses the observables that can be measured in a Coulomb-excitation experiment and their relation to the nuclear structure parameters with an emphasis on the nuclear shape. Recent examples of Coulomb-excitation studies that provided outcomes relevant for the Shell Model are also presented.

Low-Energy Coulomb Excitation for the Shell Model

Low-energy Coulomb excitation is capable of providing unique information on static electromagnetic moments of short-lived excited nuclear states, including non-yrast states. The process selectively populates low-lying collective states and is therefore ideally suited to study phenomena such as shape coexistence and development of exotic deformation (triaxial or octupole shapes). Historically, these experiments were restricted to stable isotopes. However, the advent of new facilities providing intense beams of short-lived radioactive species has opened the possibility to apply this powerful technique to a much wider range of nuclei. We discuss the observables that can be measured in a Coulomb-excitation experiment, their relation to nuclear structure parameters with an emphasis on the nuclear shape, and present some recent examples of Coulomb-excitation studies that provided outcomes relevant for the Shell Model.

New Insights into the Crystal Chemistry of Elpidite, Na2Zr[Si6O15]·3H2O and (Na1+YCax□1−X−Y)Σ=2Zr[Si6O15]·(3−X)H2O, and Ab Initio Modeling of IR Spectra

Elpidite belongs to a special group of microporous zirconosilicates, which are of great interest due to their capability to uptake various molecules and ions, e.g., some radioactive species, in their structural voids. The results of a combined electron probe microanalysis and single-crystal X-ray diffraction study of the crystals of elpidite from Burpala (Russia) and Khan-Bogdo (Mongolia) deposits are reported. Some differences in the chemical compositions are observed and substitution at several structural positions within the structure of the compounds are noted. Based on the obtained results, a detailed crystal–chemical characterization of the elpidites under study was carried out. Three different structure models of elpidite were simulated: Na2ZrSi6O15·3H2O (related to the structure of Russian elpidite), partly Ca-replaced Na1.5Ca0.25ZrSi6O15·2.75H2O (close to elpidite from Mongolia), and a hypothetical CaZrSi6O15·2H2O. The vibration spectra of the models were obtained and compared with the experimental one, taken from the literature. The strong influence of water molecule vibrations on the shape of IR spectra of studied structural models of elpidite is discussed in the paper.

Galactic halo size in the light of recent AMS-02 data

Context. The vertical diffusive halo size of the Galaxy, L, is a key parameter for dark matter indirect searches. It can be better determined thanks to recent AMS-02 data. Aims. We set constraints on L from Be/B and 10Be/Be data, and we performed a consistency check with positron data. We detail the dependence of Be/B and 10Be/Be on L and forecast on which energy range better data would be helpful for future L improvements. Methods. We used USINE V3.5 for the propagation of nuclei, and e+ were calculated with the pinching method. Results. The current AMS-02 Be/B (∼3% precision) and ACE-CRIS 10Be/Be (∼10% precision) data bring similar and consistent constraints on L. The AMS-02 Be/B data alone constrain L = 5−2+3 kpc at a 68% confidence level (spanning different benchmark transport configurations), a range for which most models do not overproduce positrons. Future experiments need to deliver percent-level accuracy on 10Be/9Be anywhere below 10 GV to further constrain L. Conclusions. Forthcoming AMS-02, HELIX, and PAMELA 10Be/9Be results will further test and possibly tighten the limits derived here. Elemental ratios involving radioactive species with different lifetimes (e.g. Al/Mg and Cl/Ar) are also awaited to provide complementary and robuster constraints.

Cryoconite: an efficient accumulator of radioactive fallout in glacial environments

Cryoconite is rich in natural and artificial radioactivity, but a discussion about its ability to accumulate radionuclides is lacking. A characterization of cryoconite from two Alpine glaciers is presented here. Results confirm that cryoconite is significantly more radioactive than the matrices usually adopted for the environmental monitoring of radioactivity, such as lichens and mosses, with activity concentrations exceeding 10 000 Bq kg−1 for single radionuclides. This makes cryoconite an ideal matrix to investigate the deposition and occurrence of radioactive species in glacial environments. In addition, cryoconite can be used to track environmental radioactivity sources. We have exploited atomic and activity ratios of artificial radionuclides to identify the sources of the anthropogenic radioactivity accumulated in our samples. The signature of cryoconite from different Alpine glaciers is compatible with the stratospheric global fallout and Chernobyl accident products. Differences are found when considering other geographic contexts. A comparison with data from literature shows that Alpine cryoconite is strongly influenced by the Chernobyl fallout, while cryoconite from other regions is more impacted by events such as nuclear test explosions and satellite reentries. To explain the accumulation of radionuclides in cryoconite, the glacial environment as a whole must be considered, and particularly the interaction between ice, meltwater, cryoconite and atmospheric deposition. We hypothesize that the impurities originally preserved into ice and mobilized with meltwater during summer, including radionuclides, are accumulated in cryoconite because of their affinity for organic matter, which is abundant in cryoconite. In relation to these processes, we have explored the possibility of exploiting radioactivity to date cryoconite.

On Line Measurement of Organic Iodine During a Severe Nuclear Accident

A severe nuclear accident may induce a dramatic dissemination of radioactive species into the environment. In that respect, improving the nuclear safety remains an important challenge to improve the society acceptability towards this energy. A solution may consist on implementing robust and reliable measurement systems operating near the Containment Venting Systems (CVS). These devices should be able to provide real time monitoring of the emitted fission products (FPs) in the course of a hypothetical accidental sequence. In the present study, a peculiar attention was devoted to iodine species (namely CH3I) measurement by complementary techniques (photoacoustic spectroscopy and gas chromatography). The most important results will be described here.

Nanomaterials for radioactive wastewater decontamination

Nanomaterials have been demonstrated to be an effective adsorbent or an ion exchanger for selectively removing various radioactive species present in contaminated water while preventing radionuclides from entering and interacting with the biosphere.

Cryoconite as an efficient monitor for the deposition of radioactive fallout in glacial environments

Cryoconite is extremely rich in natural and artificial radionuclides, but a comprehensive discussion about its ability to accumulate radioactivity is lacking. A characterization of cryoconite from two Alpine glaciers is presented and discussed. Results confirm that cryoconite is among the most radioactive environmental matrices, with activity concentrations exceeding 10,000 Bq kg−1 for single radionuclides. Atomic and activity ratios of Pu and Cs radioactive isotopes reveal that the artificial radioactivity of Alpine cryoconite is mostly related to the stratospheric fallout from nuclear weapon tests and to the 1986 Chernobyl accidents. The signature of cryoconite radioactivity is thus influenced by both local and more widespread events. The extreme accumulation of radioactivity in cryoconite can be explained only considering the glacial environment as a whole, and particularly the interaction between ice, meltwater, cryoconite and atmospheric deposition. Cryoconite is an ideal monitor to investigate the deposition and occurrence of natural and artificial radioactive species in glacial environment.

Copper-catalyzed click reactions: quantification of retained copper using 64Cu-spiked Cu(I), exemplified for CuAAC reactions on liposomes

The Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) is a powerful, highly reliable and selective reaction which allows for a rapid synthesis in high yields and under mild conditions (pH, temperature). However, the cytotoxicity of copper requires its complete removal prior to an application in vivo. This is an issue especially when it comes to CuAAC reactions on macromolecular structures or drug delivery systems, as copper might be retained by these systems. Thus, a quantification of the final copper content of these systems is inevitable, which we exemplified for a CuAAC reaction on liposomes using 64Cu-spiked Cu(I). In this respect, a Cu(II) nitrate solution was irradiated at the TRIGA Mark II research reactor Mainz to obtain c.a. [64Cu]Cu(II). The irradiated solution was directly used for a CuAAC on liposomes. After purification, their copper content was calculated utilizing γ-ray spectrometry. Only 0.018% of the added 64Cu-activity was still present in the liposome containing fractions after purification. This refers to a total amount of copper of 0.17 ng. The amount of retained copper is so low, that an in vivo application of the liposomes is absolutely reasonable. Besides this particular study, the experimental methodology may be applied to study many other CuAAC reactions, used for the synthesis of radiolabeled or non-radioactive species, which are intended for human applications.